This invention relates to an optical communication module used for transmitting and receiving optical signals or transmitting an optical signal.
In general, an optical communication module used for transmitting and receiving optical signals is provided with semiconductor optical devices of three kinds, that is to say, a semiconductor laser diode serving as a light-emitting device for an optical communication, a semiconductor photodiode serving as a light-receiving device for receiving an optical signal transmitted through an optical transmission line, and another semiconductor photodiode serving as a light-receiving device for monitoring a light power outputted from the light-emitting device.
Hitherto, the light-receiving device of a waveguide PD(photodiode) or a PIN-PD has been adopted as the light-receiving device in the optical communication module of the aforementioned kind.
A fabrication of the optical communication module is performed as follows. In case that the waveguide PD is adopted, the light-receiving device is mounted on the waveguide substrate. In case that the PIN-PD is adopted, the light-receiving device is mounted on a carrier other than the waveguide substrate, and thereafter accommodated in a module package.
However, in the conventional optical communication module, since the light-receiving device for monitoring the outputted light power receives a backward light from the light-emitting device for the optical communication, it is necessary to allocate the light-receiving device for monitoring the outputted light power near the light-emitting device for the optical communication.
As a result, positions on which the light-receiving device for monitoring the outputted light power etc. are mounted are restricted, and a degree of freedom in mounting parts is lowered.
Although xe2x80x9can optical transmitting and receiving modulexe2x80x9d and xe2x80x9ca semiconductor optical coupling device and a method for fabricating the samexe2x80x9d are respectively disclosed in Japanese patent application, laid-open, Nos. 8-190026 and 10-307221 as preceding technologies, the aforementioned problem is not solved therein.
Accordingly, it is an object of the invention to provide an optical communication module in which a light-receiving device for monitoring an outputted light power can be allocated remote from as well as near a light-emitting device for an optical communication and a degree of freedom in mounting parts can be heightened by adopting a planar divided waveguides.
It is a further object of the invention to provide an optical communication module in which a light-receiving device for monitoring an outputted light power can be allocated remote from as well as near a light-emitting device for an optical communication and a degree of freedom in mounting parts is heightened by adopting planar V-shaped waveguides.
It is a still further object of the invention to provide an optical communication module for transmitting an optical signal in which a light-receiving device for monitoring an outputted light power can allocate remote from as well as near a light-emitting device for an optical communication and degree of freedom in mounting parts can be heightened by adopting a directional coupler.
According to the first feature of the invention, an optical communication module comprises:
an optical communication substrate provide with planar divided waveguides which are optically coupled with a light-receiving device for an optical communication, a light-emitting device for the optical communication, another light-receiving device for monitoring a light power outputted from the light-emitting device and an optical fiber for the optical communication,
wherein the planar divided waveguides have such a configuration that X-shaped branch waveguides are divided by a blind slit at a crossing thereof so that said crossing is removed, and
an optical filter inserted into the blind slit.
Accordingly, an optical signal outputted from the light-emitting device for the optical communication passes through the planar divided waveguides and the optical filter, and reaches the light-receiving device for monitoring the outputted light power.
The optical filter may be inserted into the blind slit so as to be interchangeable.
Accordingly, if the optical filter is interchanged with another optical filter having a different optical transmission coefficient, a monitoring current corresponding to the different optical transmission coefficient flows into the light-receiving device for monitoring the outputted light power.
According to the second feature of the invention, an optical communication module comprises:
an optical communication substrate provided with planar V-shaped waveguides to be optically coupled with a light-receiving device for an optical communication, a light-emitting device for the optical communication, and another light-receiving device for monitoring a light power outputted from the light-emitting device, and
an optical filter which is mounted on a side surface of the optical communication substrate at a side end thereof and optically coupled with a joining portion of the V-shaped planar waveguides,
wherein the two light receiving devices are respectively allocated so as to be opposed to the optical filter, and
end faces of waveguides composing the V-shaped planar waveguides opposite to the joining portion are respectively and optically coupled with the light-emitting device and an optical fiber for the optical communication.
The light-receiving devices for the optical communication and for monitoring the outputted light power may be allocates at a predetermined distance.
Accordingly, an angle formed by the planar V-shape waveguides increases.
Moreover, both the light-receiving devices may be allocated so as to be adjacent to each other.
In this case, the angle formed by the planar V-shaped waveguides is reduced.
According to the third feature of the invention, an optical communication module comprises:
an optical communication substrate provided with a light-emitting device for an optical communication and a pair of waveguides communicated with a directional coupler which is to be optically coupled with a light-receiving device for monitoring a light power emitted from the light-emitting device, and
an optical filter which is mounted on a side surface of the optical communication substrate at a side end thereof and optically coupled with leading ends of the directional coupler at a light-receiving surface thereof,
wherein the light-receiving device is allocated so as to be opposed to the optical filter, and
end faces of the pair of the waveguides opposite to the directional coupler are respectively and optically coupled with the light-emitting device and an optical fiber for the optical communication.